Signaling apparatus



Dec. 17, 1935. R w HART 2,024,219

S IGNALING APPARATUS Filed Jan. 29, 1952 I I 1 1 I I l I Hy, y BY Patented Dec. 17, 1935 UNITED STATES PATENT OFFICE SIGNALING APPARATUS Robert Winfield Hart, Lynn, Mass., assignor to Submarine Signal Company, Boston, Mass, a

corporation of Maine The present invention relates to a system for transmitting a predetermined signal automatically and more particularly for the application of such a system in the transmission of radio signals.

In the present invention the signal transmitted is of the type described and used in my companion application Serial No. 540,961, filed May 29, 1931, and is concerned particularly with the automatic transmission of a radio signal in which a carrier wave, either of a continuous or discontinuous character, is modulated or interrupted at a low frequency, and superimposed on this modulation or interruption are signals and intervals of timed lengths. 1

There has been adopted by the Radio Telegraphic International Conference a distress or alarm signal comprising twelve dashes of four-. second duration with an interval of one second in between. This distress signal was adopted for the purpose of providing a means for automatically operating a receiving device capable of giving an alarm to anyone on a vessel so that it might be possible to notify surrounding vessels that a ship was in distress even though the radio operators on the different vessels were not on watch. The automatic apparatus adopted for the purpose of producing an alarm on the vessel has been of two distinct varieties.

One of these alarms comprises a series of timed cam mechanisms which must be operated by a fairly exact .signal or else the device will not operate at all. The purpose of this is, of course, to prevent stray signals and static from operating the alarm receiver, but in order to be assured that the alarm signal will not be operated by stray signals or static and to be operated only by the distress signal itself, the devices have been designed so that the operator must give the signal with considerable accuracy. This in ordinary operation is quite simple but under the stress of the moment, as perhaps when a vessel is sinking, the operator frequently becomes so excited that he can not transmit the signal correctly.

With the other type of alarm signal now used as illustrated in my copending application, the time duration of the signal and its interruptions need not at all be accurate and even in times of great distress, the operator ordinarily could transmit the warning signal sufiiciently well to operate the receiving device.

In order to overcome the difficulties presented in operating a distress alarm of the first type above described, I have developed a signal mech;

Figure 1. tensioned arm 20 which has a relatively high anism by which either type of automatic alarm may be operated with the same transmitted signal and without manual operation by the operator.

The device is shown in the annexed drawing 5 in which Figure 1 shows a plan View of the mechanism; Figure 2 shows a sectional view taken on the line A-A of Figure 1; and Figure 3 shows the wiring diagram of the apparatus.

There is provided in this mechanism a tuned 10 vibrating element which is adapted to vibrate at a definite fixed frequency. This is indicated in Figure 1 by the reed l9 which is operated as a make and break device by means of the current flowing through the electromagnet 2, similarly 15 as shown in my copending application referred to above. This reed may be put in operation in the manner described in the Bates application, Serial No. 578,479, filed December 2, 1931, by the operation of the cam element 30 which forces 20 the stud 33 on the reed l9 to move upwards as shown in the figure, and then suddenly releases it to allow it to vibrate freely, making contact between the elements 3| and 32. As the reed vibrates away from the magnet, the current 25 through the magnet is completed, as will be noted from the wiring diagram in Figure 3, and as the reed moves towards the magnet, the current is broken in a manner similar to the operation of the ordinary buzzer or alarm. 39

However, in the present case the reed I9 is accurately weighted by the weight 34 and provided with a definite spring tension by the spring 35 so that a definite frequency of vibration is produced. This frequency of vibration is pur- 35 posely set very low at approximately twenty seven times per second.

The reed element l9 and the contacts control a fast moving relay l shown at the bottom of This relay by means of its springnatural frequency follows the vibrations of the reed l9, thus closing and opening the electrical contact between the arm 20 and the block 2| and thereby, as indicated in the wiring diagram of Figure 3, closing and opening the transmitter circuit 35 if the keying relay 39 is closed.

This operation of the relay l impresses upon the transmitting circuit an interruption of the same nature as the vibrations effected by the reed 5 I9 and thereby produces an interrupted carrier wave at the same period. The frequency of vibration employed is approximately twenty seven times per second.

Connected in parallel across the coils of the relay 20 is the stator of the synchronous motor 31 in series, however, with the condenser ID. The interrupted direct current through the make and break of the contacts 3| and 32 produces an alternating current in the stator I5 of the frequency corresponding to the vibration of the reed in the following manner.

When the contacts 3I and 32 are closed, current flows through the magnet coil I and a voltage drop results. This voltage charges condenser II] which charging process causes a current to flow from the condenser, through the stator winding I5 back to the other side of coil I. When the contacts 3I and 32 open, condenser I0 discharges through the stator coil I5 in an opposite direction to that above. By proper choice of capacitance of the condenser III to match the inductance of I5 and I, the charge and discharge of condenser I0 result in alternating current through the stator I5.

This current drives the synchronous motor at a definite speed determined by the operation of the reed I9. The synchronous motor 31 may be of the usual type which starts automatically when current is applied to it.

In the present case a gear system, not shown, is provided with the motor in the case I6 which reduces the speed at the shaft I I to preferably one revolution per minute. Mounted on the shaft I! is the cam wheel I8 having indentations I8 spaced regularly about the circumference of the cam. Mounted at one side of the cam are the spring contact arms 24 and 25 making contact with one another through the studs at their end. At the extreme end of the spring 25 is mounted a conical element 23 adapted to engage the indentations I8 and periodically open the contact between the springs 24 and 25. The cam I8 is so divided that it has twelve divisions and the spring 25 is out of contact with the spring 24 twelve times during the minute for one second duration each time while it is in contact, as indicated in Figure 2, during the rest of the time at four second intervals. This produces exactly the international code signal. If the cam speed were faster, it is obvious that there may be fewer divisions on the cam. The only criterion is that the speed is such that the divisions may be uniform.

The indentations I8 on the cam wheel and the elements 23 are so shaped and positioned with respect to one another that if their corners wear, the time of opening or closing of the contacts will not change. Therefore, the timing remains accurate even though the points of the cam stud or cam may wear. This is accomplished by making the closing and opening occur when the flat surfaces of the cam and stud are rubbing.

The contacts 24 and 25 are connected in the keying circuit 38 to operate the keying relay 39 closing the transmitting circuit. This is preferably done by having the contacts 24 and 25 shunt the manually operated key 40 so that when the code device is put in operation, the relay key 39 will automatically be open and closed in accordance with the international code system while at the same time the low frequency interruptions will be impressed through the operation of the relay arm 20.

The wiring diagram is shown in Figure 3. The reed is energized directly from the D. C. supply line by means of the leads 9 and I3, the lead 9 going to the block 5 of the reed I9 and the lead I3 energizing the coil of the magnet 2. In series with the coils is a resistor 3 and the circuit is completed to the make and break contacts 3| and 32 and the connecting element 6. Across the make and break contact there is shunted a condenser 4 which is connected at one side to the contact 32 and at the other side to the block 5 through the lead 8. The coil of the relay I is connected through the lead I3 and the lead 6 connecting across the contact elements 3| and 32 to the direct current supply, so that the vibration of the reed I9 produces current vibrations 1 of the same frequency on the coil of the relay I. Likewise the coil of the relay I may be tuned by means of the condenser 4 which serves mainly to cut out the arcing across the contacts '3I and 32. In parallel with the coils of the relay I, as has been explained above, is the winding I5 of the stator of the synchronous motor. This is placed in series with the condenser I II. This parallel circuit may be traced from across the coils of the relay I by means of the connecting synchronous motor which, in turn, periodically closes the keying relay 39 to allow the relay 2!] which now is also operating to close and. open the circuit at the frequency of the reed. A switch may be provided, if desired, to cut the operating mechanism out of the circuit, but for ordinary purposes this is sufficiently and preferably accomplished by the use of the operating handle operating the cam 30.

Having now described my invention, I claim:

1. In a signal transmitting device in combination a tuned reed carrying one contact of a make and break device, a power supply, an operating coil for said reed connected across the power supply in series with said make and break device and a mechanical relay having a higher natural period than the reed, said relay having an operating coil connected directly across said power line in series with said make and break device.

2. In a signal transmitting device in combina tion a tuned reed carrying one contact of a make i and break device, a power supply, an operating coil for said reed connected across the power supply in series with said make and break device, a mechanical relay having a higher natural period than the reed, said relay having an operating coil connected directly across said power line in series with said make and break device and a condenser connected across said make and break device.

3. A signal transmitting device comprising, in combination, mechanical vibratory means having a definite established low frequency vibration, an electrical circuit including a make-and-break device operated by said mechanical vibrator, a synchronous motor and a condenser whereby current pulsating first in one direction, then in the reverse direction is caused to flow through the synchronous motor, a code mechanism operatively connected to said synchronous motor having means for keying a radio circuit, vibrating means operatively connected to said electric circuit for producing vibrations in synchronism with the mechanical vibrations, and keying means operated thereby connected in series with the previous keying means.

4. A signal transmitting device comprising, in

combination, mechanical vibratory means having a definite established low frequency vibration, means operated thereby for producing current pulsating first in one, then in thereverse direction, a synchronous motor having an operating coil forming a part of said means, a code mechanism operatively connected to said synchronous motor having means for keeping a radio circuit, and vibrating means operated directly through said pulsating current in synchronisrn with said mechanical means for keying the radio circuit in series with the code keying means.

5. In a signal transmitting device, in combination, a mechanical vibrating system including a tuned reed, electromagnetic means for operating said tuned reed having in its circuit a make-andbreak device mechanically controlled by said reed, a synchronous motor having its operating winding and a condenser in series therewith connected in series with the make-and-break device of said reed. and an electrically operated relay connected in shunt across the said condenser and the operating coil of the synchronous motor.

6. In combination with a transmitting circuit, a signal transmitting device comprising, in combination, a mechanical vibrating system including a tuned reed, electromagnetic means for operating said tuned reed having in its circuit a make-and-break device mechanically controlled by said reed, a synchronous motor having its operating winding and a condenser in series therewith connected in series with the make-and-break device of said reed and an electrically operated relay connected in shunt across the said condenser and the operating coil of the synchronous motor, said relay having its operating contacts controlling the transmitting circuit interrupting the same at a frequency corresponding to that of the tuned reed and means operated by the synchronous motor for impressing a code signal upon the interrupted transmitting circuit.

ROBERT WINFIELD HART. 

